Circuit breakers having electronic signal processors for detecting the occurrence of an impending overcurrent condition are currently capable of performing auxiliary circuit protection function such as undervoltage and ground fault protection, for example. One such auxiliary function is found within U.S. Pat. No. 4,672,501 entitled "Circuit Breaker and Protective Relay Unit".
U.S. Pat. No. 4,589,052 entitled "Digital I.sup.2 T Pickup, Time Bands and Timing Control Circuits for Static Trip Circuit Breakers" describes an electronic signal processor unit for determining various overcurrent conditions and interrupting a protected circuit after a predetermined time delay.
It is often helpful to provide an indication of the ON - OFF condition of a circuit breaker that is connected with industrial equipment at a location remote from the circuit breaker enclosure. One such indication is provided by means of an auxiliary switch unit whereby an indicating lamp or alarm at the location of the protected industrial equipment signals that the circuit breaker switch is in the OFF condition.
When a circuit breaker is connected within a circuit providing operating power to a sensitive manufacturing process employing robotic assembly, for example, or heat sensitive materials such as plastics, a pre-arranged shut-down procedure should be followed to prevent damage to the equipment or materials upon the occurrence of an overcurrent condition. Japanese Patent 63-031,418, published Feb. 10, 1988 describes one means for providing a warning signal upon the occurrence of a long-time overcurrent trip condition.
For purposes of this disclosure, a "long-time" overcurrent trip condition is one in which circuit interruption can be delayed for several minutes to allow the overcurrent condition to subside before interrupting a power distribution circuit. This overcurrent condition is less serious than a "short-circuit" condition which requires an immediate interruption of the circuit or a "short-time" condition which requires interruption within a few minutes to prevent damage to equipment used within the protected circuit as well as damage to the conductors within the protected circuit itself.
The present invention proposes to provide an immediate indication to an operator of a manufacturing process involving sensitive manufacturing equipment or materials that a long-time overcurrent condition is impending to thereby allow the operator to shut-down the equipment in a pre-arranged order to protect such equipment and materials. Alternatively, the invention proposes the implementation of an automatic shut-down procedure to turn off the equipment in a predetermined order upon the early indication of an impending long-time overcurrent condition or to control electricity usage for energy management purposes.